US7749623B2 - Method of controlling fuel cell system - Google Patents

Method of controlling fuel cell system Download PDF

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US7749623B2
US7749623B2 US11/080,455 US8045505A US7749623B2 US 7749623 B2 US7749623 B2 US 7749623B2 US 8045505 A US8045505 A US 8045505A US 7749623 B2 US7749623 B2 US 7749623B2
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cathode
gas
hydrogen
anode
fuel cell
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US20050271911A1 (en
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Hironori Kuriki
Hisatoshi Fukumoto
Takashi Nishimura
Hiroaki Urushibata
Hajimu Yoshiyasu
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Mitsubishi Electric Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H01M8/04228—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells during shut-down
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04303—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during shut-down
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04544—Voltage
    • H01M8/04559—Voltage of fuel cell stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
    • H01M8/04746—Pressure; Flow
    • H01M8/04753—Pressure; Flow of fuel cell reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/2457—Grouping of fuel cells, e.g. stacking of fuel cells with both reactants being gaseous or vaporised
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to methods of controlling fuel cell systems that generate electric power utilizing electrochemical reactions, and are used in, for example, electric vehicles.
  • the system has been configured in such a way that fuel gas or gas diluted with an appropriate amount of inert gas has been made to flow over an anode, inert gas has been flown over only a cathode in order to purge oxidant gas, and a resistor has been connected to the output of the fuel cell; thereby, the system has been controlled, by the resistor being connected to or disconnected from the output, so that the cell voltage has become approximately equal to EMF (electromotive force) of the theoretical hydrogen electrode concentration cell (for example, refer to Patent Document 1).
  • EMF electrostatic force
  • the oxidation degradation of the catalyst in the cathode means a phenomenon in that the catalyst included in the catalyst layer of the cathode is deactivated; specifically, when platinum catalyst particles as the catalysts are carried on carbon particles, oxygen in penetrating air reacts with the carbon particles, and the carbon particles change into carbon dioxide so that the particles are exhausted, and then, after the platinum catalyst particles have been eliminated from the carbon particles, the platinum catalyst particles aggregate with each other; consequently, due to loss of conductivity to the cathode electrode, the particles becomes inoperative as the catalyst.
  • An objective of the present invention which has been made to solve the foregoing problem, is to obtain a fuel cell system that can prevent oxidation degradation of a catalyst in a cathode thereof even if large amounts of air instantaneously penetrates into the system while the cell is paused, in which the characteristics do not deteriorate even if starting up, shutting down, and pausing the fuel cell system are repeatedly operated.
  • a method of controlling a fuel cell system includes: a step of supplying fuel gas including hydrogen to the anode, and for supplying oxidant gas to the cathode; a step, after power generation has been performed with an external load being connected between the anode and the cathode, and then the external load has been disconnected, of connecting a resistor between the anode and the cathode; a step of stopping supply of the oxidant gas; and a step of stopping supply of the fuel gas, after the potential at the cathode has dropped to equal to or lower than the potential at which hydrogen evolution starts, so as to pause the fuel cell.
  • another method of controlling a fuel cell system includes: a step of supplying fuel gas including hydrogen to the anode, and for supplying oxidant gas to the cathode; a step, after power generation has been performed with an external load being connected between the anode and the cathode, and then the external load has been disconnected, of connecting a resistor between the anode and the cathode; a step of stopping supply of the oxidant gas; and a step of pausing the fuel cell with reductant being placed into a space leading to the cathode, after the potential at the cathode has dropped to equal to or lower than the potential at which hydrogen evolution starts, so as to pause the fuel cell.
  • an atmospheric state surrounding the spaces leading to the anode and cathode can be made to be reductive while the fuel cell is paused, and even if large amounts of air mixedly penetrates into the cell instantaneously, hydrogen or reductant reacts with oxygen in air, so that the oxygen can be consumed.
  • oxidants on the surface of the catalyst formed, while the cell is paused, in the cathode can be deoxidized; thus, the catalyst can be activated.
  • FIG. 1 is a schematic view illustrating an outline of a fuel cell according to Embodiment 1 of the present invention
  • FIG. 2 is a characteristics diagram representing relationships between the number of days for DSS test and generation voltages according to Embodiment 1 of the present invention
  • FIG. 3 is a characteristic diagram representing relationships between the number of days for DSS test and generation voltages according to Embodiment 1 of the present invention
  • FIG. 4 is a schematic view illustrating an outline of a fuel cell according to Embodiment 3 of the present invention.
  • FIG. 5 is a schematic view illustrating an outline of a fuel cell according to Embodiment 5 of the present invention.
  • FIG. 6 is a schematic view illustrating an outline of a fuel cell according to Embodiment 6 of the present invention.
  • FIG. 7 is a schematic view illustrating an outline of a fuel cell according to Embodiment 7 of the present invention.
  • FIG. 1 is a schematic view illustrating a fuel cell 1 in Embodiment 1 for carrying out the present invention.
  • an anode 3 and a cathode 4 are provided on each face of a polymer electrolyte membrane 2 , and catalyst layers (not illustrated) that are electrochemical reaction fields are formed on the plane where the electrodes and corresponding faces of the polymer electrolyte membrane 2 are facing each other.
  • Separators 7 and 8 having gas flowing channels 5 and 6 , respectively, are provided outside each electrode.
  • Gas seals 9 and 10 are provided tightly encircling the anode 3 and cathode 4 .
  • Manifold holes for supplying to or exhausting from the gas flowing channels 5 and 6 fuel gas or oxidant gas, respectively, are provided on the gas seals 9 and 10 , and an oxidant-gas supplying line 11 , a fuel-gas supplying line 12 , an oxidant-gas exhausting line 13 , and a fuel-gas exhausting line 14 are connected to each of the manifold holes.
  • the oxidant-gas supplying line 11 and oxidant-gas exhausting line 13 are connected to the flowing channel 6 for supplying with the oxidant gas the cathode 4 , meanwhile the fuel-gas supplying line 12 and fuel-gas exhausting line 14 are connected to the flowing channel 5 for supplying with the fuel gas the anode 3 .
  • An oxidant-gas supplying-amount adjusting means 15 is connected to the oxidant-gas supplying line 11 so as to enable the supplying amount of the oxidant gas to be adjusted, meanwhile a fuel-gas supplying-amount adjusting means 16 is connected to the fuel-gas supplying line 12 so as to enable the supplying amount of the fuel gas to be adjusted.
  • an oxidant-gas exhausting-amount adjusting means 17 and a fuel-gas exhausting-amount adjusting means 18 are connected to the oxidant-gas exhausting line 13 and the fuel-gas exhausting line 14 , respectively.
  • the polymer electrolyte membrane 2 a polymer electrolyte membrane having proton conductivity, gas barrier characteristics, and electrical insulation characteristics is used; for example, a polymer electrolyte membrane consisting of a perfluorinated backbone and a sulfonic group is used.
  • the catalyst layer is composed of, for example, metallic microparticles such as platinum catalyst particles that are carried on carbon particle surfaces and have catalytic activity, and polymer binders; moreover, additives such as polymer particles are mixedly added as the need arises. These additives are used for controlling the hydrophilic properties or the hydrophobic properties, or controlling the porosity, of the catalyst layer.
  • the layers are, for example, directly formed on the surfaces of the polymer electrolyte membrane 2 , formed by layers being transferred onto the surfaces of the polymer electrolyte membrane 2 after having been formed on the surfaces of another substrates, or the catalyst layers are jointed to the polymer electrolyte membrane 2 after the layers having been formed on the surfaces of the anode 3 and the cathode 4 .
  • the gas permeability and the electrical conductivity are needed; therefore, they are generally composed of a carbon fiber such as carbon paper or carbon cloth.
  • the separators 7 and 8 for example, a carbon board having a minute structure and electrical conductivity is used, and ditches are provided so as to form the flowing channels 5 and 6 .
  • the fuel cell 1 is connected to a resistor 21 through a switch 20 , between the anode 3 and the cathode 4 .
  • the separators 7 and 8 are composed of, for example, a carbon board having electrical conductivity
  • the resistor 21 is connected between the separator 7 stacked on the anode 3 and the separator 8 stacked on the cathode 4 .
  • the effective area (the area in which the catalyst layer is formed) of the anode 3 or cathode 4 is approximately 100 cm 2 .
  • the utilization is defined by a ratio of the gas amount utilized in the electric generation and the supplied amount of the gas.
  • all means including the oxidant-gas supplying-amount adjusting means 15 , fuel-gas supplying-amount adjusting means 16 , oxidant-gas exhausting-amount adjusting means 17 , and fuel-gas exhausting-amount adjusting means 18 are adjusted in such a way that the fuel gas and oxidant gas flow with a needed gas flowing amount.
  • the fuel cell 1 was brought into a normal operation state with the cell being switched from the resistor 21 to an external load 19 by the switch 20 .
  • the generated voltage of the fuel cell 1 was 0.73 V when the system started to operate.
  • the power generation of the fuel cell 1 was shut down through the following procedure.
  • the load between the anode 3 and cathode 4 was at first changed from the external load 19 to the resistor 21 (30 m ⁇ ) by the switch 20 , and then the oxidant-gas supplying-amount adjusting means 15 and oxidant-gas exhausting-amount adjusting means 17 were closed so that the flow rate became nil ml/min.
  • oxygen in the air remaining in the cathode 4 reacts with hydrogen to produce water, only nitrogen remains mostly in the oxidant-gas supplying line 11 connected to the cathode 4 .
  • the potential of the cathode 4 gradually decreases, and then becomes 0.1 V or less due to the increasing of the concentration polarization based on the oxygen diffusion-rate determination.
  • the anode 3 and cathode 4 the following reactions occur, and a hydrogen/hydrogen concentration cell is formed; resultantly, hydrogen is evolved.
  • the potential of the cathode at this time is referred to as a hydrogen evolution potential.
  • the potential in which hydrogen starts to evolve is determined by the Nernst equation (1), and varies with temperature, hydrogen gas concentration, etc.
  • E ⁇ ( RT/ 2 F )ln( P H2-c /P H2-a ) (1)
  • E denotes a generated voltage
  • R denotes the gas constant
  • T denotes temperature
  • F denotes the Faraday constant
  • P H2-c denotes a partial pressure of hydrogen in the cathode
  • P H2-a denotes a partial pressure of hydrogen in the anode.
  • the hydrogen evolution potential was 0.1 V or less.
  • the potential is preferably decreased not more than 0.05 V
  • the potential is preferably decreased not more than 0.05 V
  • because hydrogen is supplied from the fuel-gas supplying line 12 , a space leading to the anode is filled with hydrogen.
  • the fuel-gas supplying-amount adjusting means 16 and fuel-gas exhausting-amount adjusting means 18 were closed so that the hydrogen gas flow rate became nil ml/min.
  • the gas supplying/exhausting lines to the anode and cathode that is, the gas-amount adjusting means 15 , 16 , 17 and 18 are blocked, and the spaces leading to the cathode and anode each are in a sealed state; however, even in an extreme case in which air mixedly penetrated into the spaces leading to the anode and cathode, according to this embodiment, measures can be taken to prevent the oxidation degradation of the electrodes. That is, if air mixedly penetrates into the space leading to the cathode, oxygen in the air is consumed by a redox reaction with hydrogen existing in the space leading to the cathode.
  • the hydrogen is oxidized into a hydrogen ion in the anode, and the hydrogen ion moves through the electrolyte membrane, and then is deoxidized into hydrogen in the cathode; consequently, equilibrium is maintained between the electrodes.
  • the interiors of both electrodes are maintained in an atmosphere always filled with hydrogen. After the fuel cell has been maintained in this state, the fuel cell starts to operate.
  • the interior-atmosphere of the electrodes just before the operation was measured by gas chromatography analysis, resulting in the hydrogen concentration of 70 vol. %.
  • a test (DSS test: daily start up and shut down test), in which, after 8 hours continuous generation per day was performed, according to the above described procedure, the fuel cell was shut down and maintained therein for 16 hours, was repeatedly performed for 100 days, and then generated-voltage variation over time in the fuel cell was measured.
  • DSS test daily start up and shut down test
  • generated voltage of the fuel cell was measured in such a method that the cell ran 4 hours after its generation started and then the generated voltage was measured every day.
  • FIG. 2 is a view illustrating a generated-voltage variation of the fuel cell according to DSS test; as a result, the generated voltage has scarcely decreased for 100 days.
  • the cathode of the fuel cell lays in a relatively high potential and is exposed in the oxidation atmosphere during the operation, as in this embodiment, by the cathode potential being decreased so as to evolve hydrogen during the cell pause, the cathode comes into a state of a reductive atmosphere due to the evolved hydrogen. Therefore, even if oxides that can decrease the electrochemical reactivity evolve on the faces of the catalysts in the cathode catalyst layer during the operation, the reduction processing is performed during the cell pause; consequently, there is an effect of the cathode catalysts being activated again.
  • the cathode is made to be at low-potential to evolve hydrogen with the oxidant-gas supplying being shut down, in a state in which water is not produced, a humidified gas uniformly streams over the surface of the anode, resulting in an effect of the water distribution being uniformized in the polymer electrolyte membrane.
  • FIG. 3 is a view illustrating generated-voltage variation of the fuel cell according to this DSS test; a voltage of approximately 0.05 V decreased for 50 days.
  • air and hydrogen were used as the oxidant gas and the fuel gas, respectively; however, as the oxidant gas, oxygen gas, mixed gas that is mixture of inert gas and oxygen gas, etc., can be used other than air, meanwhile, as the fuel gas, hydrogen gas including carbon-dioxide obtained by reforming methanol, kerosene, etc. can be used other than hydrogen gas.
  • the control method has been explained in which the fuel cell is composed of a pair of the cathode and anode as illustrated in FIG. 1 ; however, in a fuel cell stackingly configured in such a way that the anode-side separator 7 where the fuel gas flowing channel 5 is provided is placed on the side of the anode 3 , and the cathode-side separator 8 where the oxidant-gas flowing channel 6 is provided is placed on the side of the cathode 4 , and then the anode 3 , separators 7 and 8 , cathode 4 are stacked, the same control method as that in this embodiment can be also applied.
  • the external load 19 has a load-control function for controlling the load so that the fuel cell 1 can generate constant current of approximately 25 A, stable generation characteristics can be maintained, in which the current does not vary.
  • the space leading to the anode and the space leading to the cathode were filled with mixed gas of hydrogen and nitrogen while the cell was paused; thus, the cell was in pause states in which the hydrogen concentration of this mixed gas was made to be five kinds of nil, 0.1, 0.5, 3.0, and 10.0 vol. %.
  • the DSS test was repeated for 100 days similarly to that in Embodiment 1, and generated-voltage variation over time was investigated.
  • the conclusion of the degradation rates in each of the cells is represented in table 1.
  • the degradation rate represents the decreasing amount of the generated voltage before and after the DSS test.
  • FIG. 4 is a schematic view illustrating a fuel cell according to Embodiment 3.
  • an aluminum gas pack 22 is connected to the fuel-gas supplying line 12 as a mechanism for supplying fuel gas.
  • V a ( V a ⁇ C H2-a ⁇ 2 ⁇ T R )/( V a +V c ) (2) Therefore, in equation (2), when the other parameters (C H2-cell , V a , V c , and T R ) are set to certain specified values, V a can be designed by suitably selecting the volume of the gas pack 22 so that the hydrogen concentration (when the cell starting up) of C H2-cell in the space leading to the anode and the space leading to the cathode becomes equal to or higher than 0.1 vol. %.
  • Embodiment 1 by closing the gas-amount adjusting means for supplying to/exhausting from the cathode the oxidant was consumed with the oxidant-utilizing rate being made infinite; however, as a method of increasing the oxidant-gas utilization, a method of replacing the gas on the cathode side with an inert gas that does not include oxidant is also available.
  • Embodiment 4 a fuel cell similar to that in Embodiment 1 was used.
  • Gases that do not include oxidant can be selected from those including inert gases such as argon and carbon dioxide, water vapor, and hydrocarbon such as methane, other than nitrogen.
  • the gas-amount adjusting means 15 , 16 , 17 and 18 on the gas supplying/exhausting lines of the anode and cathode were in a closed state; thereby the space leading to the anode and the space leading to the cathode were maintained in a hermetically sealed state filled with hydrogen.
  • the DSS test was repeated for 100 days similarly to that in Embodiment 1, so that generated-voltage variation over time in the fuel cell was measured. As a result, the generated voltage decreased little for 100 days.
  • the cathode of the fuel cell that is at relatively high potential during the operation is exposed in the oxidation atmosphere; however, the cathode comes into a reductive atmospheric state, due to, as with the embodiment, hydrogen produced by the cathode potential being decreased during the cell pause. Therefore, even if oxide, which can deteriorate the electrochemical reactivity, evolves on the faces of the catalysts in the cathode catalyst layer during the operation, the reduction processing is performed during the cell pause; consequently, there is an effect of the cathode catalysts being activated again.
  • FIG. 5 is a schematic view illustrating a fuel cell 1 according to Embodiment 5.
  • elements similar to those in Embodiment 1 are represented by the same numerals.
  • a fling-gas supplying line 23 is connected to the line through a filling-gas supplying-amount adjusting means 24 .
  • the fling-gas supplying-amount adjusting means 24 is closed. After 100 hours of continuous operation, at first, the load between the anode 3 and cathode 4 was changed from the external load 19 to the resistor 21 using the switch 20 , and then the oxidant-gas supplying-amount adjusting means 15 and oxidant-gas exhausting-amount adjusting means 17 were closed so that the air flow rate was nil ml/min.
  • the cathode of the fuel cell that is at relatively high potential during the operation is exposed in the oxidation atmosphere; however, the cathode comes into a reductive atmospheric state, due to hydrogen produced by the cathode potential being decreased during the cell pause. Therefore, even if oxide, which can deteriorate the electrochemical reactivity, evolves on the faces of the catalysts in the cathode catalyst layer during the operation, the reduction processing is performed during the cell pause, resulting in an effect of the cathode catalysts being activated again.
  • FIG. 6 is a schematic view illustrating a fuel cell 1 according to Embodiment 6.
  • elements similar to those in Embodiment 1 are represented by the same numerals.
  • a gas pack 33 is connected to the oxidant-gas supplying line 11 through a gas-amount adjusting means 32 as illustrated in FIG. 6 .
  • Reductant 34 is contained in the gas pack 33 .
  • the reductant 34 for example, zinc metal powder can be used.
  • a method of controlling the fuel cell 1 configured as described above is explained. Because the generation method for the fuel cell 1 is the same as that in Embodiment 1, a method of shutting down and pausing the cell is explained here.
  • the gas-amount adjusting means 32 is closed during generation. After 100 hours of continuous operation, the load between the anode 3 and cathode 4 was at first changed from the external load 19 to the resistor 21 using the switch 20 , and then the oxidant-gas supplying-amount adjusting means 15 and oxidant-gas exhausting-amount adjusting means 17 were closed so that the air flow rate was nil ml/min.
  • the gas-amount adjusting means 32 was opened so that the oxidant-gas supplying line 11 and the gas pack 33 conducted to each other; moreover, by adjusting the fuel-gas supplying-amount adjusting means 16 the fuel-gas supplying line 12 was adjusted so that the fuel-gas supplying line 12 was almost filled with the fuel gas under approximately the same pressure as atmospheric pressure, and thus the fuel cell 1 was paused.
  • the DSS test was repeated for 100 days similarly to that in Embodiment 1, generated-voltage variation over time in the fuel cell was measured. As a result, the generated voltage decreased little for 100 days.
  • the cathode of the fuel cell that is at relatively high potential during the operation is exposed in the oxidation atmosphere; however, the cathode comes into a reductive atmospheric state, due to hydrogen produced by the cathode potential being decreased during the cell pause. Therefore, even if oxide, which can deteriorate the electrochemical reactivity, evolves on the faces of the catalysts in the cathode catalyst layer during the operation, the reduction processing is performed during the cell pause, resulting in an effect of the cathode catalysts being activated again.
  • the zinc metal powder is used as the reductant; however, another material can also be used as far as it is more easily oxidized than the electrode material.
  • a solid material such as magnesium metal powder, alkaline-metal powder of lithium, sodium, etc., liquid material such as oxalic acid aqueous solution, or gas material such as methane gas, hydrogen disulfide gas, etc. can also be used.
  • FIG. 7 is a schematic view illustrating a fuel cell 1 according to Embodiment 7.
  • the gas pack containing the reductant was connected only to the oxidant-gas supplying line through the gas-amount adjusting means; however, in this embodiment, the gas pack 33 is connected to the oxidant-gas supplying line 11 and the fuel-gas supplying line 12 through the gas-amount adjusting means 32 and a gas-amount adjusting means 35 , respectively, as illustrated in FIG. 7 .
  • the reductant 34 are contained in the gas pack 33 .
  • the reductant 34 for example, zinc metal powder can be used.
  • both the gas-amount adjusting means 32 and 35 are closed.
  • the fuel cell 1 was shut down, by closing the fuel-gas supplying-amount adjusting means 15 , the oxidant-gas supplying-amount adjusting means 16 , the oxidant-gas exhausting-amount adjusting means 17 , and the fuel-gas exhausting-amount adjusting means 18 , the fuel-gas supplying line 11 and oxidant-gas supplying line 12 were hermetically sealed, and the gas-amount adjusting means 32 and 35 were opened so that both the fuel-gas supplying line 11 and the oxidant-gas supplying line 12 conducted to the gas pack 33 , and thus the cell was paused.
  • the cathode of the fuel cell that is at relatively high potential during the operation is exposed in the oxidation atmosphere; however, the cathode comes into a reductive atmospheric state, due to hydrogen produced by the cathode potential being decreased during the cell pause. Therefore, even if oxide, which can deteriorate the electrochemical reactivity, evolves on the faces of the catalysts in the cathode catalyst layer during the operation, the reduction processing is performed during the cell pause, resulting in an effect of the cathode catalysts being activated again.
  • Embodiment 5 and Embodiment 8 because the oxidant-gas supplying line 11 or fuel-gas supplying line 12 needs to be supplied with fuel gas under approximately atmospheric pressure during the cell pause, fuel gas is consumed a little; however, in this embodiment, because the fuel gas need not be supplied during the cell pause, the preserving procedure becomes simple in low-cost.
  • the zinc metal powder is used as the reductant
  • a solid material such as magnesium metal powder, alkaline-metal powder of lithium, sodium, etc.
  • liquid material such as oxalic acid aqueous solution
  • a gas material such as methane gas, hydrogen disulfide gas, etc. can also be used as other materials.
  • Embodiment 8 is configured in such a way that, in Embodiment 7, the gas pack 33 is configured using a vessel that is flexible and hermetically sealable, for example, made of rubber, without the reductant 34 .
  • the generation is performed by the fuel cell in a state in which the gas-amount adjusting means 35 is closed, meanwhile the gas-amount adjusting means 32 is opened. Thereby, fuel gas is supplied from the fuel-gas supplying line 12 into the gas pack 33 , and the flexible gas pack 33 becomes inflated under the supplying pressure of the fuel gas.
  • the fuel-gas supplying-amount adjusting means 15 When the fuel cell was shut down, by closing the fuel-gas supplying-amount adjusting means 15 , the oxidant-gas supplying-amount adjusting means 16 , the oxidant-gas exhausting-amount adjusting means 17 , and the fuel-gas exhausting-amount adjusting means 18 , the fuel-gas supplying line 11 and the oxidant-gas supplying line 12 were hermetically sealed, and the gas-amount adjusting means 32 and 35 were opened, so that both the fuel-gas supplying line 11 and the oxidant-gas supplying line 12 conducted to the gas pack 33 , and thus the cell was paused.
  • the cathode of the fuel cell that is at relatively high potential during the operation is exposed in the oxidation atmosphere; however, the cathode comes into a reductive atmospheric state, due to hydrogen produced by the cathode potential being decreased during the cell pause. Therefore, even if oxide, which can deteriorate the electrochemical reactivity, evolves on the faces of the catalysts in the cathode catalyst layer during the operation, the reduction processing is performed during the cell pause, resulting in an effect of the cathode catalysts being activated again.
  • the gas pack 33 is composed of the flexible vessel, even if the fuel-gas supplying line 11 and the oxidant-gas supplying line 12 come under a reduced-pressure state in response to temperature drop when the fuel cell is shut down, fuel gas is supplied from the gas pack 33 , resulting also in an effect of preventing air penetrated from the exteriors. Furthermore, in Embodiment 5 and Embodiment 6, because fuel gas needs to be supplied to the oxidant-gas supplying line 11 or the fuel-gas supplying line 12 under approximately atmospheric pressure during the cell pause, the fuel gas is consumed a little; however, in this embodiment, because the fuel gas need not be supplied during the cell pause, the preserving procedure becomes simple in low-cost.
  • the interior volume of the gas pack 33 is determined so that sufficient volume of fuel gas can be stored to deoxidize and exhaust oxygen in the penetrated air.
  • the gas pack may be configured to contain reductant.
  • the ability to consume oxygen against the air penetrated during the cell pause may further increase.
  • fuel gas is supplied to the gas pack 33 through the fuel-gas supplying line, the fuel gas may be supplied from those other than the fuel-gas supplying line, for example, from another hydrogen cylinder.
  • Embodiment 1 fuel cells in which resistance of the resistor 21 was varied at 15, 25, 30 (Embodiment 1), 50 and 80 m ⁇ were made; then, DSS test was carried out for 100 days in the generating and pausing methods similar to those in Embodiment 1, and the decreasing amounts of the generated voltages after the DSS test were measured, comparing the amounts to those measured before the DSS test. In this case, the external load having the loading control function similar to that in Embodiment 1 was used. The relationships between resistances of the resistor 21 and decreasing amounts of the generated voltages are listed in table 2.
  • the resistance of the resistor whose connection is switched from the external load to the cell when the fuel cell is shut down needs to be determined in a suitable range.
  • the limiting value of the resistance in the lower side is explained.
  • the resistance R ( ⁇ ) of the resistor may be equal to or higher than (A/B) ⁇ (C/100). If the resistance is equal to or higher than this value, when the connection is switched from the external load 19 to the resistor 21 , the gas utilization cannot exceed 100%, resultantly the state of the fuel gas shortage does not occur.

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JP5151035B2 (ja) * 2006-02-03 2013-02-27 日産自動車株式会社 燃料電池システム
JP5406968B2 (ja) * 2006-03-10 2014-02-05 Ｊｘ日鉱日石エネルギー株式会社 燃料電池の活性化方法、および燃料電池用活性化装置
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JP5190749B2 (ja) * 2006-11-22 2013-04-24 トヨタ自動車株式会社 燃料電池システム
JP4956226B2 (ja) * 2007-02-27 2012-06-20 東芝燃料電池システム株式会社 燃料電池発電システムの停止保管方法およびプログラム並びに燃料電池発電システム
DE102007014760A1 (de) * 2007-03-28 2008-10-02 Robert Bosch Gmbh Vorrichutng und Verfahren zur Erzeugung elektrischer Energie
US20080292921A1 (en) * 2007-05-22 2008-11-27 Balasubramanian Lakshmanan Recovery of inert gas from a fuel cell exhaust stream
JP5261999B2 (ja) * 2007-07-03 2013-08-14 富士電機株式会社 燃料電池発電装置
JP5169056B2 (ja) * 2007-07-31 2013-03-27 日産自動車株式会社 燃料電池システム及びその運転停止方法
JP5471010B2 (ja) * 2008-09-04 2014-04-16 日産自動車株式会社 燃料電池システムおよび燃料電池システムの制御方法
DE102009045952A1 (de) 2008-11-12 2010-05-20 Robert Bosch Gmbh Wirkungsgradoptimierter Niedriglastbetrieb von Brennstoffzellensystemen
JP5364492B2 (ja) * 2009-01-23 2013-12-11 株式会社東芝 燃料電池発電システム
JP5796227B2 (ja) 2010-03-18 2015-10-21 パナソニックＩｐマネジメント株式会社 燃料電池発電システム及び燃料電池発電システムの運転停止方法
JP5786531B2 (ja) * 2011-08-02 2015-09-30 アイシン精機株式会社 燃料電池システム
KR101405551B1 (ko) * 2012-08-01 2014-06-10 현대자동차주식회사 연료전지 성능 회복 방법
KR101326484B1 (ko) * 2012-08-09 2013-11-08 현대자동차주식회사 연료전지 스택의 부분 활성화 방법
JP6252459B2 (ja) 2014-12-12 2017-12-27 トヨタ自動車株式会社 燃料電池の検査方法

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